Lubricating oils



United States Patent i R 2,897,152 1 LUBRICATING OILS 11 Claims. 01.252-415 This invention is for improvementsinor relatingv to lubricatingoils and is particularly concerned with lubri- 2,897,152 Patented July-28,

ice.

should not interfere in any way with the normal functions of the twoforegoing classes of additive. Many turbine oils, especially marineturbine oils used by the Admiralty, are controlled as regards oxidationstability,

salt water corrosion of ferrous metals,- demulsification value andcorrosive action on cuprous metals, by a very rigid specification. It isnecessary, therefore, that extreme pressure additives incorporatedtherein should not adversely alfect compliance with its clauses.

Many of the more commonly employed extreme pres sure additives aredetrimental in one or more respects. Thus chlorine compounds generallytend to promote oxe idation and are also prone to hydrolysis with thesubeating oils which are to be usedunder conditions which tend todisrupt the lubricant film, which disruption'more particularly takesplace'when the pressure between the bearing surfaces is very great.There have already been provided lubricants which have a'highload-carrying capacity. Such lubricants are generally known in the tradeas extreme pressure lubricants.

A large number of organic compounds have been pro posed for use asextreme pressure agents, including var ious types of organic diandpolysulphides, and the cor responding derivatives of selenium. While thehigher polysulphides are very effective in increasing-the film rupturestrength of the oil in which they are'dissolved, they tend to beinherently unstable, corrosive', especia1ly to copper and cuprousmaterials and to exert a pro oxidant efiect on the oil. The disulphides,on the other hand, and other sulphur compounds containing relativelyfirmly-bound sulphur, though comparatively non-corrosive to copper,usually possess rather poor. extreme'presv sure properties insuflicientto warranttheir use-except in conjunction with other extreme as organichalogen compounds; compounds there have beendisclosed as additives forlubricating oils various simple alkyl and aryl -thiocarbonates andthiocarbamates.

pressure additives such Among this class of It is a nobject of thepresent invention toprovide lubricating compositions having extremepressure properties containing additives which are considerably lesscorrosive to copper and cuprous materials than many known extremepressure agents of comparable loadcarrying ability. h

It is a further object of the invention to provide lubricatingcompositions having improved resistance to oxida tion and foam-forming.i

It is yet a further object of the inventionto provide sequent liberationof hydrochloric acid which accelerates rusting of ferrous'metal parts. 1

Many sulphur compounds are also pro 0xidant,-and those which are withouteffect in this respect usually possessinadequate extreme pressureproperties.

We have found a class of organic sulphur compounds which possesssurprisingly effective extreme-pressure properties and which at the sametime have valuable anti: oxidant properties and foam-inhibitingproperties, which are relatively inactive towards copper and cuprousmetals and which "do not increase ferrous metal corrosion oremulsification in the presence of water.

According to the present invention there is provided alubricatingcomposition comprising a mineral lubricating oil base and a minorproportion of a compound having the formulaz' 1 e i 1.

N. -s-R.oooR, v Rf v where R and R are alkyl, aryl, cycloalkyl radicalsor where R and R are hydrocarbon radicals, preferably CH and R is analkyl, aryl or cycloalkyl radical. 7.

It is necessary to select R R d R so thatlthe resulting product isoil-soluble in the proportions in which it is to be employed. PreferablyR is CH;.;- and R R and R are alkyl radicals, the sum of'the carbonatoms in R R and R being at least six.

additives for turbine oils capable of increasing substantially theirload-carrying capacity without at the same time increasing theirtendency to oxodise or emulsify with water. I

Thus at the present time many oils used for turbine lubrication consistof specially selected mineraloil blends stabilised against oxidation bythe incorporation of antioxidant additives and containing also additivesdesigned to protect ferrous metal parts against rusting or corrosion by,e.g. sea water. 'It is of course important that additional additives,incorporated in such oils tor the purpose of enhancing their extremepressure properties,

If desired the radicals R R or R may contain halogen substituents, butwhen the additives are to be employed in turbine oils, the presence ofhalogen is to be avoided.

It would appear that the presence of ester groups situated in the alphaposition to the dithiocarbamate group exerts an activating influencewith the consequent pro-. duction of extreme pressure propertiessubstantially in excess of those obtainable by the use of the simplealiphatic or aromatic dithiocarbamates.

Examples ofsuitable compounds falling 'within'i'the above formulainclude: n-Butyl (dimethyl dithiocarbamyl) acetate, n-Butyl (di-n butyldithiocarbamyl) acetate, n-Butyl (di isopro'pyl dithiocarbamyl) acetate,

Isopropyl (di-n-butyl dithiocarbamyl) acetate, Z-ethyl hexyl(cyclopentamethylene dithiocarbamyl) acetate CHrCHg SN.CSCHr-OOOCHifilH-CHICHZCH CH;

CHr-C g C2115 10 percent may be employed, but in general from about 0.5percent to about 2.0 percent is contemplated, especially for use inturbine oils. When it is desired merely to impart antioxidant propertiesto an oil, smaller proportions of the additives may be employed, e.g.from 0.05 to 0.5. In a preferred form of the present invention the additives may be employed in steam turbine oils, especially in marineturbine oils. v i The turbine oils to which the additives of the presentinvention may be added may contain additional antioxidant additiveswhich maybe of the alkylated phenol type, e.g. tertiary butyl cresol,2:4 dimethyl-6-tertiary butyl phenol or 2:6 di-tertiary butyl-p-cresol,and will also normally contain antirusting additives which may be ofvarious types, one such class of additives being the acid esters of thelong chain mono-esters of polyhydric alcohols described in Britishpatent specification No. 643,025. V

7 When the lubricants of the present invention are to be employed atrelatively high temperatures it is desirable to include therein acopper-staining inhibitor. Thus there may be included in the lubricant aminor proportion of a mercapto-arylene-thiazole or a derivative thereof,or an alkyl thiuram disulphide, or an additive or combination ofadditives of the type disclosed in United States patent applicationSerial No. 507,147, now US. Patent No. 2,836,561. The copper-staininginhibitor is a cyclic compound capable of homolytic dissociation intofree radicals A preferred subclass of inhibitors of this type are2-mercaptobenzothiazole and its derivatives such as benzothiazoledisulphide, hydroxy methyl thiobenzothiazole .and triphenyl methylthiobenzothiazole, but the corresponding derivatives of otherZ-mercaptothiazoles may be employed, all as disclosed in myaforementioned application Serial No. 507,147.

The additives of the present invention may, if desired, be employed inconjunction with organic halogenated compounds in mineral lubricatingoils to provide, for example, extreme pressure lubricants for hypoidgears. An example of a suitable organic halogenated compound ischlorinated parafiin wax which may be employed in an amount from 1 to15% by Weight. Oils containing such combinations of additives arecapable of withstanding higher loads than oils which contain only thesulphur compound. As already stated, however, the presence of halogencompounds in turbine oils is undesirable.

" 'Specific examples of lubricating compositions prepared in accordancewith the present invention are:

EXAMPLE 1 I A turbine oil having enhanced load-carrying capacity at 140F. t

and complying with British Admiralty Specifications OM. 100 wasprepared, consisting of approximately:

% of a mineral oil having a viscosity of about 170 seconds Redwood at140 F.

25% of a solvent refined mineral oil having a viscosity of about 65seconds Redwood at 140 F.

to which was added- 1.5% n-butyl (dimethyl dithiocarbamyl) acetate0.015% alkylated succinic acid type ferrous metal corrosion inhibitor0.001% calcium petroleum sulphonate EXAMPLE 2 A turbine oil havingexcellent oxidation resistance and resistance. to corrosion of ferrousmetals in the presence of salt watervconsisted of:

59% of a highly. refined mineral oil having a viscosity of about 65seconds Redwood at 140 F.

41% of a highly refined mineral oil having a viscosity of about 170seconds Redwood at 140 F. i

to which blend was added- 0.1% n-butyl (dimethyl dithiocarbamyl) acetate0.01% of an alkylated succinic acid type ferrous metal .corrosioninhibitor 0.001% calcium petroleum sulphonate This blend had a viscosityof about seconds Redwood EXAMPLE 3 An extreme pressure hypoid rearv axlelubricant, conforming to the Society of Automotive Engineers (SAE)classification grade 140, had the following approximate Composition: v i

75 conventionally-refined Mid-Continent oil of viscosity about 750seconds Redwood at F.

15 1 solvent refined mineral oil of viscosity seconds Redwood'at 140 F.

8% chlorinated parafi'in wax (approx. 40% chlorine) 2%n-butyl(di-n-butyl dithiocarbamyl) acetate EXAMPLE 4 goodresistance tooxidation and corrosion of ferrous metals in presence of salt water,good resistance to foam ingand improved resistance to the corrosion ofcopper andicuprous metalsat elevated temperatures, consisted of thecomposition of Example 1, to which was added- 0.1% -benzothiazoledisulphide 0.1% zinc di-n-butyl dithiocarbamate The preparation ofn'-butyl (dimethyl dithiocarbamyl) acetate 1s Illustrative of thegeneral method of preparing the compounds of the present invention.

Preparation of n-bzttyl (dimethyl dithiocarbamyl) acetate To a solutionof 279 grams (1.85 mols) of n-butyl monochloracetate in an equal volumeof alcohol was added very slowly with vigorous stirring at roomtemperature-940 mls. (2.3mols) of 30.9% w./w. aqueous solutionof'sodi-umdim'ethyl dithiocarbamate expanded with an'equal volume ofalcohol An exothermic reaction-took'place and sodium chloride separatedtogether with a heavy oily liquid. The reaction was completed by warmingthe mixture to 70" C. Distilled water was now added to dissolve thesodium chloride, andthe product, which crystallised on standing andscratching, was filtered, off. H a i v I I';' Ihe yield was 375 grams(87% oftheoretical). M.P 30 C; after. recrystallisation from, petroleumether.

llercentsa -7-2; h p c' 7 Other esters prepared from the correspondingch1orace-;.

tates and sodium dithiocarbamates included: Ethyl" (dimethyldithiocarbamyl) acetate, crystalline solid, MP. 61 C.

with a rubbing ratio of 3.4 to 1, loading being applied manually inincrementsv of 5. lb. (scalereading) every seconds until failure tookplace.

The additives were dissolved in a mineral oil blend such as Oil B whichconsisted of 80% of a solvent-re- 0 r0 dimeth 1 dithiocarbaml acetatesolid er- I Is g 2(86; thegretical, 28.9% n (p 5 guild mniieral oilhavmg a viscosity of about 150 seconds Isobu 1 dm eth l dithiocarbam lacetate .0 stalline 6 9 140 i of solvent'refined g y y) I W eral 011having a viscosity of about seconds Redwood 140 F. Iso r0 1 di-n-bu 1dithiocarbam l acetate, low meltat ty I .0 y A very similar base oil,011 A, consisted of the two mg sohd (percent N, 4.34, theoretical, 4.74)10 a1 H d d n-Butyl (di-n-butyl dith'ioca'rbamyl) acetate, light ambermmer 0 e m Example 1 m -20 F liquid (percent S, 203; thematica1,v 201)had a viscosity index of about 60 whereas 011 B =had a 2-ethyl hexyl(cyclopentamethylene dithiocarbamyl) acevlscosltymfdex 01595-- l I tate,amber oil, t S, 16 0;theoretica1, 19.37) In certain blends marked withan asterisk an alkylated Phenyl '(di-n-butyl dithiocarbamyl') acetate,brown il 5 succinic acid type ferrous metal corrosion inhibitorwas(percent S, 18.2; theoretical, 18.9) I also Present n-Butyl u(dimethyldithiocarbamyl) isobutyrate (percent The results of load-carrymg testsare summarized in I S, 21.8; theoretical, 24.3) Table 1.

Four-ball machine tests Percent SAE- sulphur SOD Tg3t"'Ba59 providedLoad, 1 a Mean wear Mean test No. 011 Additlvespresent. the Kg, at Weld(mms) at Hertz failure additive incipient point, load load seizure Kg.(lbs.)

100 150 Kg. Kg.

'1 None Nil 32/30 2.9 11 as 2 'B n-Butyl (dimethyl dithlocarbamyl)acetate, (0.75%) -1-.- 0. 20 95/100 220 1.9 2.2 41 3 B n-Butyl(dlmethyl' dithiocarbamyl) acetate (1.0%) 0. 26 95/100 210 1,3 22 45 130A .n-Butyl (dimethyldithiocarbamyl) acetate (l.5%) 0. 39 90/95 190 1. 4v2.0 "A- 'n-Butyl (di-n-butyldithiocarbamyl) acetate (2.0%)--- 0.40 85/90200/220 1.9 2.1

B Isopropyl (di-n-butyl dithiocarbamyl) acetate (2.0%)" 0. 40 90/95230 1. 7' 2.0 B Phenyl (di-nbutyl dithiocarbamyl) acetate (2.15%)--- 0.40 110 220 0. 5 2.0 B 2-ethyl hexyl (cyclopentamethylenedithiocarbarnyl) acetate (2.5%)- 0. 40 120' 250 0.6 2.0 B n-Butyl a(dlmethyl-dithiocarhamyl) isobutyrate (1.05%) 0.36. 85/130 200 0.0 1.8 Bflachloroethyl (di-n-butyl dithiocarbamyl) acetate (2.0%) 0. 40 95/100230 0.7 1.8 B S-n-hexyldi-n-butyl dithiocarbamate (1.92%). 0. 40 75/80200 1.8 2.1 13* S-n-hexyl di-n-butyl dithiocarbamate (1.25%)- 0. 2075/80 2. 0 2. 5 30 120 A Di-benzyl disulphide (1.0%) 0.26 60/70 260 1.01.5 135 In an attempt to prepare B-chloroethyl (di-n-b-utyldithiocarbamyl) acetate from /ihloroethyl monochloracetate and sodiumdi-n-butyl dithiocarbamate, an amber oil was obtained containing 8.7% Cl(theoretical, 11.1%). This evidently consisted of a mixture ofcompounds, some of the terminalchlorineatoms having been replaced. 0fthe foregoing compounds, the first three listed were not soluble to theextent of 1.0 percent in mineral oil blend A, as used in the majority ofthe tests herein described.

' T 0 demonstrate the. efie'otiveness of the compounds used in thecompositions of the present invention as extreme pressure agents, testswere carried out on the well known four-ball machine similar to thatdescribed by Boerlage in .Engineering, 13th July 1933, volume 136, page46. This apparatus comprised four steel balls arranged in the form of apyramid.- The top ball was held in a chuck attached to a spindlerotating at approximately 1500 ppm. and pressed against the three bottomballs clamped in a stationary ball holder. The balls were immersed inthe oil to be tested. Tests were normally run for one minute at a seriesof difierent loads, but in certain cases supplementary tests werecarried out for a duration of ten seconds, the Mean Hertz Load" beingcalculated by the standard procedure described in U.S. FederalSpecification VV-L-79ld Method 650.3 (1950).

I Certain tests were also carried out on the well known Society ofAutomotive Engineers (S.A.E.) Testing Machine described by Neely in theJournal of the Society pf. Automotive Engineers, volume 39, page 293(1936), by a modified procedure known as the S.A.E.S.O.D. test,described byMcTurk in Wright Aeronautical Development Centre (W.A.D .C.)Technical Report 53-88, page (1953), published by the U.S. Department ofCommerce, Ofiice of Technical Services. In test pror a s-m9 A- tiw na ar rea t 0. 0 -P-m:

In Table 1 tests '2 to 10 summarize the load-carrying properties of avairety of lubricating oils prepared in ac cordance with the presentinvention, from which it will be seen that in all cases theload-carrying'capacity of the base oil (test 1) 'is greatly increased bythe presence of organic dithiocarbamyl acetates. Tests 11 and, 12 givecomparative figures obtained with a simple conventional organicdithioca-rbamate, while test 13 quotes similar figures for dibenzyldisulphide, a well known extreme pressure additive known to be among themost efiective of the simple organic disulphides.

It will be seen by comparing tests 2, 3, l2 and, 13 that n-butyl(dimethyl dithiocarbamyl) acetate, which is typical of the additives ofthe present invention, gave significantly better results on the fourball machine than both the conventional dithiocarbamates and dibenzyldisulphide, although the total amounts of added sulphur in the oils wereidentical in tests 3, l2 and 13 and'less in test 2. In this connectionit should be pointed out that the load at the point of incipient seizureand the mean Hertz load are generally believed to be the most sig'nificant of the four ball machine test results quoted.

By comparing test 11 with tests 4 to 10 (all about .40% added S) it willagain be seen that the simple thiocarbamate ester was inferior to thecompounds of the present invention.

When used in turbine oils, the organic dithiocarbamyl acetates not onlydo not adversely affect the properties of such oils but confervaluable'antioxidant' and antifoaming properties, thus renderingunnecessary the addition of specific antioxidant and antifoamingadditives. If special load-carrying properties are not required, quitesmall amounts of the dithiocarbamyl acetates are sulficient to confer adegree of oxidation, and foaming sta:

im)" a t TABLE 2 Oxidation test Foaming test (76 F.) Acidity (milli-Demul- Acidity Saltwater Test Additive Base grams sificaafterDemulsicorrosion No. oil KOH tion oxidation fication Tendpar value (mgs.value eney Stability (mls.) gram) KOH after oxi- (mls.) per dation gram)14 None A 0. 06 Failed, unless anti- N o rusting 490 Nil (8 mins).oxidant present. n-Butyl (dimethyl dithiocarbamyl) acetate (1.5%)" A0.06 0.11 do 10 N11 (10 sees). 16... n-Butyl (dimethyldithiocarbamyl)acetate (0.75%) B 0.11 630 do Nil N 17 n-Butyl (dimethyldithiocarbamyl)acetate (0.1%) A 0.22 110 N11 (2 mins.). 18 n-Bntyl (di-n-butyldithiocarbamyl) acetate (2.0%). A 0.08 240 No rusting 19.--" n-Butyl(dimethyl dithiocarbamyl) acetate (1.0%), B 0.17 600 do Ni.l'(1.5mins.).

Benzothiazole disulphide (0.1%). 20.-. As test 19+0.1% zinc di-n-butyldithiocarbamate B 0. 11 360 do 400 Nil (6 mins.).

Table 2 illustrates the effect of the additives on typ1- temperatures, aselection of the results belng given in cal turbine oils containing rustinhibitors which, with the 20 Table 3.

TABLE 3 [Tests recorded in this table were 24 hours duration, the baseoil used throughout being oil B*] Appearance of copper strips atgestAdditives present 21 n-Butyl (dimethyl dithiocarbamyl) Light brown/pea-Dark peacock] Dark peacock Dark brown- Dark peacock, acetate (0.75%).cock stain. magenta. brown; 10% black. black patch. at one end. 22 Astest No. 21+0.1% benzothiazole Orange brown powdisulphide. dery deposit.23"--- As test N o. 22+0.1% zinc di-n-butyl Reddish brassy Light goldenPatch of yellow Light peacock Powdery light dithiocarbamate. stain.brow-n. deposit. with powdery brown deposit; light brown deposit.

There was no stain of the copper during 3 hours at 100 0. by n-butyl(dimethyl dlthiocarbamyl) acetate in concentrations up to at least 1.5%,

the absence of copper deactivators.

addition of a suitable antioxidant, would comply with British AdmiraltySpecification O.M. 100.

In test 17 the foaming test was carried out using as base oil the higherviscosity component of oil A without rust inhibitors.

The methods employed for determining the various values quoted abovewere standard methods described in Standard Methods for TestingPetroleum and its Products, and having the following references:

Acidity I.P. 1/53 Method A (page 12, 1943 edition) Demulsification valueI.P. 19/51 (page 117, 1951 edition) Oxidation test I.P. 114/53 P (page395, 1953 edition) Salt water corrosion test I.P. 135/51 (page 390, 1951edition) (modified to comply with OM. 100 specification) Foamingstability I.P. 146/55 T (page 266, 1956 edition) (sequence 1 only quotedin the above table) It will be seen from Table 2 that dithiocarbamylacetates function effectively as antioxidants even in quite lowconcentrations, thus enabling turbine oils to satisfy the oxidationrequirements of QM. 100 specification (0.20 mg. KOH per gram maximumafter oxidation test) without the addition of any other oxidationinhibitors.

By comparing tests 15 to 17 and 19 with test 14, it will be seen thatthey also function effectively as inhibitors of foaming. In test 20, thepresence of zinc di-n-butyl dithiocarbamate evidently interfered withthis eifect.

Other properties of the oils, such as acidity, demulsification value andsalt-water corrosion resistance were unafi'ected by the addition of thedithiocarbamylacetates.

In order to determine the elTect of the lubricating oils of the presentinvention on copper. at various temperatures, a series of tests werecarried out in which strips of clean electrolytic quality copper foil 2inches long and /2 inch wide were immersed in the oils in test tubes andheated in an oven for various periods of time at different From Table 3it will be seen that n-butyl'(dimethyl dithiocarbarnyl) acetate, whichis typical of the additives of the present invention, is very mild inits action towards copper at temperatures of the order of to C. such asare encountered in steam turbines. Further improvement, particularly atthe higher temperatures, may be obtained by including benzothiazoledisulphide or a combination of this compound with zinc di-n-lbutyldithiocarbamate. 1

A turbine oil complying with British Admiralty Specification O.M. 100and consisting of base oil B containing 1.0% n-butyl (dimethyldithiocarbamyl) acetate together with rust inhibitors as in Example 1and copper deactivators as in Example 4 was subjected to a test on thewell known Institution of Automobile Engineers (I.A.E.) 3 A" CentresGear Machine described by Mansion in the Journal of the Institute ofPetroleum, volume 38, page 633 (1952). This machine was operated at 4000rpm. using En. 34 gears, with an oil temperature of 70 C. The averagefailure load was 93 lbs, a typical 0.M. 100 turbine oil withoutload-carrying additive failing at 29 lbs.

To,illustrate the use of dithiocanbamyl acetates in extreme pressurelubricants suitable for hypoid gears, the composition of Example 3 wastested on the four ball machine (standard one minute run), the weldpoint being 490-500 kg. and the mean wear scar diameter at 100, 200, 300and 400 kg. load being respectively 0.5, 1.2, 1.7 and 2.3 mms.

A commercially available hypoid gear oil having approximately the sameviscosity and complyingwith US. Army Specification MILL2105 welded at400 kg, the mean Wear scar diameter at 100, 200 and 300 kg. load beingrespectively 0.4, 1.5 and 2.0 ms.

We claim: I 1. A lubricating composition, consisting essentially of amineral lubricating oil base containing 'from"0;05

percent up to 10 percent by weight of a compound having the formula: 7

where X is selected from the group consisting of R1 and R2 hydrocarbonchain of nitrogen atom so as to form a ring structure, from the groupconsisting of -CH being lower alkyl radicals, and an aliphatic fivecarbon atoms attached to the R is selected 8 XNJL-S-RCOOR:

Where X is an aliphatic hydrocarbon chain of five carbon atoms attachedto the nitrogen atom so as to form a ring structure, R is selected fromthe group consisting of 'CH2,

Bui t-H and where R; and R are lower alkyl radicals, and R is selectedfrom the group consisting of a phenyl radical and an alkyl radicalcontaining no more than eight carbon atoms.

4. A lubricating composition as claimed in claim 1, wherein R containshalogen substituents.

5. A lubricating composition consisting essentially of a minerallubricating oil base containing from 0.05 percent up to 2 percent byweight of n-butyl (dimethyl dithiocarbamyl) acetate.

6. A lubricating composition consisting essentially of "10 a minerallubricating oil base containing from 0.0519 0.5 percent by weight of acompound having the formula: a. s

N.CS-OHaCO0R| R: where R and R are lower alkyl radicals and R is'aualkyl radical containing not more than eight carbon atoms.

7. A steam turbine oil' consisting essentially of a mineral lubricatingoil base containing from 0.5 to 2 percent by weight of a compound havingthe formula:

5 X'Nlfll-S-RCOOR:

where X is selected from the group consisting of R. R and R being loweralkyl radicals, and an aliphatic hydrocarbon chain of five carbon atomsattached to the nitrogen atom so as to form a ring structure, R isselected from the group consisting of CH where R; and R are lower alkylradicals, and R is selected from the group consisting of a phenylradical and an alkyl radical containing no more than eight carbon atoms.

8. A steam turbine oil consisting essentially of a mineral lubricatingoil base containing from 0.5 to 2 percent by weight of a compound havingthe formula:

where R and R are lower alkyl radicals and R is an alkyl radicalcontaining no more than eight carbon atoms.

9. A steam turbine oil as claimed in claim 7, wherein there is includedfrom 0.005 to 0.1 percent by weight of an anti-rusting additive selectedfrom the group consisting of an acid ester of a long-chain monoester ofa polyhydric alcohol, and an alkylated succinic acid.

10. A steam turbine oil as claimed in claim 7, wherein there is includedfrom 0.01 to 0.5 percent by weight of a copper-staining inhibitorselected from the group consisting of Z-mercapto benzothiazole and aderivative thereof capable of homolytic dissociation into free radicals11. A lubricating composition consisting essentially of a minerallubricating oil base containing from 0.05 percent up to 10 percent byweight of a compound having the formula:

s XNJ'l-S-ILCOOR;

where X is selected from the group consisting of Elli 12 R and R beinglower alkyl radicals, and an aliphatic Where R and R 'are lower alkylradicals, and R is hydrocarbon chain of five carbon atoms attached toselected from the group consisting of a phenyl radical the nitrogen atomso as to form a ring structure, R is and an alkyl radical containing nomore than eight selected from the group consisting of -CH carbon atoms,and from 1 to 15 percent by weight of '5 a chlorinated paraflin wax.

R4(|)H v g V References Cited in the file of this patent v UNITED STATESPATENTS L 2,160,851 Faust June 6, 1939 1 2,160,880 Loane June 6, 1939

1. A LUBRICATING COMPOSITION CONSISTING ESSENTIALLY OF A MINERALLUBRICATING OIL BSE CONTAINING FROM 0.05 PERCENT UP TO 10 PERCENT BYWEIGHT OF A COMPOUND HAVING THE FORMULA: